1. Technical Field
The present invention relates to a method for manufacturing semiconductor devices in general, and in particular to a method for manufacturing programmable fuses. Still more particularly, the present invention relates to a method for manufacturing a programmable chalcogenide fuse within a semiconductor device.
2. Description of the Prior Art
Redundancy circuitry is typically employed to improve the yield of integrated circuits that fail due to localized defects. For example, when a memory cell has a defect that prohibits functionality, a redundant circuit can be switched in via a physical disconnection of a wiring element, commonly known as a fuse, via laser energy. Such programming of redundant circuits is usually performed during the manufacturing process and is hidden from users.
Programmable fuses are often utilized to implement redundancy repair on memory devices or to provide lot identification. A commonly used programmable fuse structure in a memory device is comprised of electrically conductive materials such as aluminum, copper, or polysilicon. A programmable fuse within a memory device can be programmed, i.e., blown open, with a laser beam. Typically, the programming of a fuse within a memory device is performed by guiding a laser beam over a fuse matrix within the memory device to convert a failing address file into a functional address file. The laser beam has sufficient energy to evaporate the conductive fuse and permanently program (or xe2x80x9cblowxe2x80x9d) the programmable fuse into an electrically and physically open condition. One drawback of such method is the requirement of additional tools, such as lasers with steppers, and programming algorithms, which adds delays to manufacturing. Another drawback is that some programmable fuses, such as titanium tungsten fuses, have been known to grow back under certain conditions, which creates a huge reliability problem. However, the major drawback associated with the above-mentioned programmable fuse is that those fuses cannot be reprogrammed. In other words, once a fuse has been evaporated, the fuse cannot be reused again.
Consequently, it is desirable to provide a method for manufacturing an improved programmable fuse within a semiconductor device. The improved programmable fuse is re-programmable and is reasonably easy to implement.
In accordance with a preferred embodiment of the present invention, a resistor is initially formed on a substrate. Then, a chalcogenide fuse is formed on top of the resistor. Finally, a conductive layer is deposited on top of the chalcogenide fuse for providing electrical conduction to the chalcogenide fuse.
All objects, features, and advantages of the present invention will become apparent in the following detailed written description.